1. Field of the Invention
The present invention relates generally to pressure gauges and more particularly to an improved pressure gauge including a movable piston pressure sensing element and a gauge calibration element.
2. Description of the Prior Art
The most commonly used dial pressure gauge is the Bourdon-Tube gauge. It includes a flattened tube made of resilient bronze or steel that is bent generally into a curved shape that is typically an arcuate section of a circle. One end of the flattened tube is engaged to the pressure inlet of the gauge. When fluid pressure is applied to the gauge inlet, the arcuate flattened tube tends to straighten out, and the distal end of the tube moves proportionally to the pressure difference between the inside and outside of the tube. The distal end of the tube is engaged to a pressure scale pointer through a pinion and spur tooth gear. A spring is engaged to the pinion to provide a reactive force. The Bourden-Tube gauge must be properly calibrated to ensure accuracy, and it can be costly and time consuming to accurate calibrate a Bourden-type gauge with its various mechanisms.
One embodiment of the present invention is designed to be similar in size and shape to the Bourden-type gauge, to act as a replacement for it. The present invention generally utilizes a piston-type pressure element having a coil spring to provide a reactive force. Gauges of this general configuration are known in the prior art, and they too need to be calibrated. The present invention utilizes a threaded calibration nut that is fixedly engaged following calibration to produce accurate results.